The present invention relates to a novel method and apparatus for making phosphors.
The phosphors which have traditionally been used are prepared by synthesis under rigid conditions and by means of skilled techniques. The general method for preparing phosphors involves adding traces of activators consisting of various elements which can become luminescent centers, such as silver, arsenic, copper, europium, manganese, phosphorus, lead, antimony, tin and zinc, to base materials that can become phosphor host materials, such as oxide, sulfide, halide and oxysalt of barium, beryllium, calcium, cadmium, sodium, magnesium, strontium, yttrium, zinc and the like, then suitably adding a flux, such as halogenated alkali, in order to facilitate entrance of the activator into the base crystals and finally heating and baking these materials in a fully regulated and controlled atmosphere at 700.degree. to 1300.degree. C. for several tens of minutes to a few hours. In other words, the conventional method of preparing phosphors requires such severe preparation-step control conditions as heating and baking in a fully controlled atmosphere for an extended period of time at an elevated temperature that risk of decomposition of the base material itself actually becomes a problem.